Two pharmacologically and physiologically distinct lateral inhibitory networks in the inner retina contribute to the receptive field surround of ganglion cells and can be identified with stimuli that are stationary or moving. Sustained lateral inhibition (SLI), which is elicited by steady illumination, is responsible for the spatial tuning of ON ganglion cells. It is not known if this inner retinal pathway also alters the sensitivity of ganglion cell or to what extent it is modulated during changes in adaptational state. Transient lateral inhibition (TLI), which is activated at the onset and offset of illumination, becomes sustained when illumination is continuously changing either intensity or location. TLI is weak or disabled in the dark-adapted retina, and is potentiated over several minutes during light adaptation. Neither the site of modulation nor the modulator underlying this slow potentiation is known. The proposed research will examine novel aspects of the cellular mechanisms creating these two forms of lateral inhibition in the inner retina and will improve our understanding of how these systems are modulated during changes in the retinal state of adaptation.